I'm writing a story where an alien race of refugees comes to Earth and through their pollen they spread a virus. This virus was in fact, genetically engineered by the aliens as a means to propagate their seed.
The virus is engineered to activate under specific atmospheric conditions. The virus is ingested/transmitted via contact with the pollen. It acts by extracting necessary genetic material from the hosts' cells to fertilize/germinate in Earth's atmospheric conditions.
Obviously this isn't hard sci-fi here. I know this is far-fetched, I just need a vaguely plausible explanation/mechanism by which this could possibly work written in some scientific sounding jargon.